Ma Xuanxuan, Liu Sujing, Liu Ying, Gu Guodong, Xia Chuanhai
School of Resources and Environmental Engineering, Ludong University, Yantai 264025, China.
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.
Sci Rep. 2016 Apr 26;6:25068. doi: 10.1038/srep25068.
Catalytic hydrodehalogenation (HDH) has proved to be an efficient approach to dispose halogenated aromatic compounds (HACs). Liquid-phase HDH of single and mixed halobenzenes/4-halophenols with H2 over 5% Pd/C and Raney Ni catalyst are investigated and compared. For liquid-phase HDH of single HACs, hydrogenolytic scission reactivity of C-X bonds decreases in order of C-Br > C-Cl > C-I > C-F over Pd/C catalyst, and in order of C-I > C-Br > C-Cl > C-F over Raney Ni catalyst. To clarify the reason why hydrogenolytic scission reactivity of C-X bonds over Pd/C and Raney Ni catalysts exhibits different trends, liquid-phase HDH of mixed HACs over Pd/C and Raney Ni catalysts were studied, and catalysts are characterized by SEM, EDX, and XRD techniques. It was found that the high adsorption of iodoarenes on Pd/C catalyst caused the HDH reactivity of iodoarenes to be lower than that of chloroarenes and bromoarenes in the HDH of single HACs. Moreover, the adsorption of in situ produced iodine ion (I(-)) to catalyst surface would result in the decline of catalytic activity, which might be the main reason why the HDH reactivity of HACs in the presence of NaI is rather low.
催化加氢脱卤（HDH）已被证明是处理卤代芳烃（HACs）的一种有效方法。研究并比较了单卤代苯/4-卤代酚和混合卤代苯/4-卤代酚在5% Pd/C和雷尼镍催化剂上与氢气的液相加氢脱卤反应。对于单一组分HACs的液相加氢脱卤反应，在Pd/C催化剂上，C-X键的氢解断裂反应活性按C-Br＞C-Cl＞C-I＞C-F的顺序降低；在雷尼镍催化剂上，则按C-I＞C-Br＞C-Cl＞C-F的顺序降低。为了阐明在Pd/C和雷尼镍催化剂上C-X键的氢解断裂反应活性呈现不同趋势的原因，研究了混合HACs在Pd/C和雷尼镍催化剂上的液相加氢脱卤反应，并采用扫描电子显微镜（SEM）、能量散射X射线光谱（EDX）和X射线衍射（XRD）技术对催化剂进行了表征。研究发现，在单一组分HACs的加氢脱卤反应中，碘代芳烃在Pd/C催化剂上的高吸附导致碘代芳烃的加氢脱卤反应活性低于氯代芳烃和溴代芳烃。此外，原位生成的碘离子（I(-)）吸附到催化剂表面会导致催化活性下降，这可能是在NaI存在下HACs加氢脱卤反应活性相当低的主要原因。
